1. Field of the Invention
This invention relates generally to gas turbine engine exhaust nozzles and, more particularly, to gas turbine engine exhaust nozzle seals with segmented basesheets.
2. Description of Related Art
Military aircraft gas turbine engines often include variable geometry exhaust nozzles. The variable geometry exhaust nozzle varies throat and exit areas of the exhaust nozzle using flaps and seals. Examples of such engines are the General Electric F110 and the F414. The flaps and seals define the flowpath and the seals, as their name implies, seal against adjacent flaps. Because the exhaust nozzles are subjected to high temperatures and thermal gradients as a result of hot combustion gases exiting the engine, the variable geometry nozzle must maintain a coherent flowpath while shielding nozzle structural components.
Nozzle divergent flaps and seals incorporating backbones to secure the basesheets have been used for the divergent section of convergent/divergent variable geometry nozzles. A flowpath surface of the seal basesheet is exposed to hot combustion gases in an exhaust stream of the nozzle, while a backside of the seal is in a cooler environment. The temperature differential causes distortion and premature wear fatigue failure. It is desirable to have good sealing between the divergent seal and its adjacent flaps, while allowing for movement in the axial or longitudinal direction, while restraining the basesheet segments in the radial and transverse directions to eliminate the cause of distortion in the radial direction. It is desirable for longitudinally adjacent segments to allow local movement relative to each other due to thermal differential between the flowpath surface and the backside along with the thermal differential between the centerline and the axial edges. It is desirable for the segmented design to free up the center of the seal between the segments, so the movement does not accumulate over the length of the seal or cause distortion leading to premature wear or fatigue, while still providing good sealing with the adjacent flaps.